Dear ERT WG,
Apologies to be late on this Last Call comment, we hope that you would
still take this into account. The (editorial) comment is on the HTTP
Vocabulary in RDF 1.0 document[1].
As you may know, the RDFa 1.1 specification (see [2] for its latest
version) provides a very flexible ways for the usage of URI-s and
Compact URI-s. Essentially, if an RDFa attribute is used like this:
<.... rel="pref:ref" ...>
then the processing algorithm:
- decides whether a URI has been associated with 'pref', in which case
the final URI is the concatenation of that URI with 'ref'
- otherwise, the pref:ref is considered to be a URI, and that will be
used for in the final, generated RDF
This approach has a caveat: there may be issues if somebody defines a
prefix 'pref' when 'pref' is also a defined URI scheme, and RDFa
authors are advised not to do that. (Actually, some RDFa tools may
also raise warnings if this happens.)
Another information is that RDFa 1.1 defines the notion of an RDFa
default profile; essentially, a number of prefixes are pre-defined for
any RDFa 1.1 file. The exact content of the prefixes is still under
consideration (see [3]) but it is fairly well accepted that any RDF
vocabulary, defined as a W3C Recommendation (or note) will end up,
eventually, in this list. In particular, the early, pointer methods,
the content, and the HTTP vocabularies will fall under this rule when
finalized.
However, the current HTTP Vocabulary document uses 'http' as its
prefix in all the examples; the same prefix is also used in the EARL
Schema document[4]. For the reasons outlined above, the choice of this
prefix would be a mistake for RDFa, hence the plan to use the 'ht'
prefix[3] in the RDFa default profile. In our view, it would be much
better if the same prefix was adopted in the original specification
documents, too; we believe, regardless of the RDFa issues, that it is
not a good practice to reuse the name of a well-known URI scheme for
vocabulary abbreviation.
On a similar, though less important issue: there has been some
discussions with the Dublin Core Metadata Initiative (DCMI) on the
prefix that should be adopted for the dcterms vocabulary (see the
thread starting at [5]). The final advise we got from DCMI is to use
the prefix 'dc' for http://purl.org/dc/terms/ in the default RDFa
profile[6]. You may consider using it, too, for the sake of
consistency, but that is clearly at the discretion of the Working
Group.
Best,
Thomas Steiner
In the name of the RDFWA Working Group
[1] http://www.w3.org/TR/2011/WD-HTTP-in-RDF10-20110510/
[2] http://www.w3.org/TR/2011/WD-rdfa-core-20110331/
[3] http://www.w3.org/profile/rdfa-1.1
[4] http://www.w3.org/TR/2011/WD-EARL10-Schema-20110510/
[5] http://lists.w3.org/Archives/Public/public-rdfa-wg/2011Jun/0015.html
[6] http://lists.w3.org/Archives/Public/public-rdfa-wg/2011Jun/0037.html
--
Thomas Steiner, Research Scientist, Google Inc.
http://blog.tomayac.com, http://twitter.com/tomayac